Dynamics of impurity attraction and repulsion of an intrinsic localized mode in a driven 1-D cantilever array.

Both low frequency and high frequency impurity modes have been produced in a SiN micromechanical cantilever array by illumination with either an infrared or visible laser. When such laser-induced impurities are placed near a driven intrinsic localized mode (ILM), it is either repelled or attracted. By measuring the linear response spectrum for these two cases, it was found that vibrational hopping of the ILM takes place when the natural frequency of the ILM and an intrinsic even symmetry linear local mode are symmetrically located about the driven ILM frequency so that parametric excitation of these two linear modes is enhanced, amplifying the lateral motion of the ILM. Numerical simulations are consistent with these signature findings. It is also demonstrated that the correct sign of the observed interaction can be found with a harmonic lattice-impurity model but the magnitude of the effect is enhanced in a nonlinear lattice.

Experimental observation of the bifurcation dynamics of an intrinsic localized mode in a driven 1D nonlinear lattice.

Linear response spectra of a driven intrinsic localized mode in a micromechanical array are measured as it approaches two fundamentally different kinds of bifurcation points. A linear phase mode associated with this autoresonant state softens in frequency and its amplitude grows as the upper frequency bifurcation point is approached, similar to the soft-mode kinetic transition for a single driven Duffing resonator. A lower frequency bifurcation point occurs when the four-wave-mixing partner of this same phase mode intercepts the top of the extended wave branch, initiating a second kinetic transition process.

Effects of interleukin 12 on immune responses and host protection in mice infected with intestinal nematode parasites.

The cytokine interleukin (IL) 12 stimulates T cell and natural killer cell production of interferon (IFN) gamma and inhibits T cell production of IL-4. We investigated the effects of IL-12 on cytokine gene expression, immunoglobulin (Ig)E, mucosal mast cell, and eosinophil responses, and the course of infection in mice inoculated with the nematode parasite Nippostrongylus brasiliensis, as well as the IFN-gamma dependence of these effects. IL-12 stimulated IFN-gamma and IL-10 gene expression during primary and secondary N. brasiliensis infections and inhibited IL-3, IL-4, IL-5, and IL-9 gene expression during primary infections but had little inhibitory effect during secondary infections. IL-12 inhibited IgE, mucosal mast cell, and blood and tissue eosinophil responses during primary infections, but only eosinophil responses during secondary infections. IL-12 enhanced adult worm survival and egg production during primary, but not secondary infections. IL-12 needed to be administered by day 4 of a primary infection to inhibit IgE and mucosal mast cell responses, and by day 6 to strongly inhibit eosinophil responses and to enhance worm survival and fecundity. Anti-IFN-gamma mAb inhibited the effects of IL-12 on IgE secretion, intestinal mucosal mastocytosis, and parasite survival and fecundity, but did not affect IL-12 inhibition of eosinophilia. These observations indicate that IL-12, if administered during the initiation of eosinophilia. These observations indicate that IL-12, if administered during the initiation of an immune response, can change the response from one that is characterized by the production of T helper (Th)2-associated cytokines to one characterized by the production of Th-1 associated cytokines. However, IL-12 treatment has less of an effect once the production of Th2-associated cytokines has become established. In addition, our results provide evidence that Th2-associated responses protect against, and/or Th1-associated responses exacerbate, nematode infections.

Antitumor and antimetastatic activity of interleukin 12 against murine tumors.

It has recently been demonstrated that in vivo administration of murine interleukin 12 (IL-12) to mice results in augmentation of cytotoxic natural killer (NK)/lymphocyte-activated killer cell activity, enhancement of cytolytic T cell generation, and induction of interferon gamma secretion. In this study, the in vivo activity of murine IL-12 against a number of murine tumors has been evaluated. Experimental pulmonary metastases or subcutaneous growth of the B16F10 melanoma were markedly reduced in mice treated intraperitoneally with IL-12, resulting in an increase in survival time. The therapeutic effectiveness of IL-12 was dose dependent and treatment of subcutaneous tumors could be initiated up to 14 d after injection of tumor cells. Likewise, established experimental hepatic metastases and established subcutaneous M5076 reticulum cell sarcoma and Renca renal cell adenocarcinoma tumors were effectively treated by IL-12 at doses which resulted in no gross toxicity. Local peritumoral injection of IL-12 into established subcutaneous Renca tumors resulted in regression and complete disappearance of these tumors. IL-12 was as effective in NK cell-deficient beige mice or in mice depleted of NK cell activity by treatment with antiasialo GM1, suggesting that NK cells are not the primary cell type mediating the antitumor effects of this cytokine. However, the efficacy of IL-12 was greatly reduced in nude mice suggesting the involvement of T cells. Furthermore, depletion of CD8+ but not CD4+ T cells significantly reduced the efficacy of IL-12. These results demonstrate that IL-12 has potent in vivo antitumor and antimetastatic effects against murine tumors and demonstrate as well the critical role of CD8+ T cells in mediating the antitumor effects against subcutaneous tumors.

Water exchange between the subglacial Lake Vostok and the overlying ice sheet

It has now been known for several years that a 200-km-long lake, called Lake Vostok, lies beneath the ice sheet on which sits Vostok Station in Antarctica. The conditions at the base of the ice sheet above this subglacial lake can provide information about the environment within the lake, including the likelihood that it supports life. Here we present an analysis of the ice-sheet structure from airborne 60-MHz radar studies, which indicates that distinct zones of basal ice loss and accretion occur at the ice-water interface. Subglacial melting and net ice loss occur in the north of the lake and across its 200-km-long western margin, whereas about 150 m of ice is gained by subglacial freezing in the south. This indicates that significant quantities of water are exchanged between the base of the ice sheet and the lake waters, which will enrich the lake with gas hydrates, cause sediment deposition and encourage circulation of the lake water.

Copurification of actin and desmin from chicken smooth muscle and their copolymerization in vitro to intermediate filaments.

Desmin is a 50,000-mol wt protein that is enriched along with 100-A filaments in chicken gizzard that has been extracted with 1 M KI. Although 1 M KI removes most of the actin from gizzard, a small fraction of this protein remains persistently insoluble, along with desmin. The solubility properties of this actin are the same as for desmin: they are both insoluble in high salt concentrations, but are solubilized at low pH or by agents that dissociate hydrophobic bonds. Desmin may be purified by repeated cycles of solubilization by 1 M acetic acid and subsequent precipitation by neutralization to pH 4. During this process, a constant nonstoichiometric ratio of actin to desmin is attained. Gel filtration on Ultrogel AcA34 in the presence of 0.5% Sarkosyl NL-97 reveals nonmonomeric fractions of actin and desmin that comigrate through the column. Gel filtration on Bio-Gel P300 in the presence of 1 M acetic acid reveals that the majority of desmin is monomeric under these conditions. A small fraction of desmin and all of the actin elute with the excluded volume. When the acetic acid is removed from actin-desmin solutions by dialysis, a gel forms that is composed of filaments with diameters of 120-140 A. These filaments react uniformly with both anti-actin and anti-desmin antiserum. These results suggest that desmin is the major subunit of the muscle 100-A filaments and that it may form nonstoichiometric complexes with actin.

Physical Conditions of Fast Glacier Flow: 3. Seasonally-Evolving Ice Deformation on Store Glacier, West Greenland.

Temporal variations in ice sheet flow directly impact the internal structure within ice sheets through englacial deformation. Large-scale changes in the vertical stratigraphy within ice sheets have been previously conducted on centennial to millennial timescales; however, intra-annual changes in the morphology of internal layers have yet to be explored. Over a period of 2 years, we use autonomous phase-sensitive radio-echo sounding to track the daily displacement of internal layers on Store Glacier, West Greenland, to millimeter accuracy. At a site located ∼30 km from the calving terminus, where the ice is ∼600 m thick and flows at ∼700 m/a, we measure distinct seasonal variations in vertical velocities and vertical strain rates over a 2-year period. Prior to the melt season (March-June), we observe increasingly nonlinear englacial deformation with negative vertical strain rates (i.e., strain thinning) in the upper half of the ice column of approximately -0.03 a-1, whereas the ice below thickens under vertical strain reaching up to +0.16 a-1. Early in the melt season (June-July), vertical thinning gradually ceases as the glacier increasingly thickens. During late summer to midwinter (August-February), vertical thickening occurs linearly throughout the entire ice column, with strain rates averaging 0.016 a-1. We show that these complex variations are unrelated to topographic setting and localized basal slip and hypothesize that this seasonality is driven by far-field perturbations in the glacier's force balance, in this case generated by variations in basal hydrology near the glacier's terminus and propagated tens of kilometers upstream through transient basal lubrication longitudinal coupling.

Synthesis and Assay of SIRT1-Activating Compounds.

The NAD(+)-dependent deacetylase SIRT1 plays key roles in numerous cellular processes including DNA repair, gene transcription, cell differentiation, and metabolism. Overexpression of SIRT1 protects against a number of age-related diseases including diabetes, cancer, and Alzheimer's disease. Moreover, overexpression of SIRT1 in the murine brain extends lifespan. A number of small-molecule sirtuin-activating compounds (STACs) that increase SIRT1 activity in vitro and in cells have been developed. While the mechanism for how these compounds act on SIRT1 was once controversial, it is becoming increasingly clear that they directly interact with SIRT1 and enhance its activity through an allosteric mechanism. Here, we present detailed chemical syntheses for four STACs, each from a distinct structural class. Also, we provide a general protocol for purifying active SIRT1 enzyme and outline two complementary enzymatic assays for characterizing the effects of STACs and similar compounds on SIRT1 activity.

Tailoring enzymes that modify nonribosomal peptides during and after chain elongation on NRPS assembly lines.

Nonribosomal peptide synthetases are large enzyme complexes that synthesize a variety of peptide natural products through a thiotemplated mechanism. Assembly of the peptides proceeds through amino acid loading, amide-bond formation and chain translocation, and finally thioester lysis to release the product. The final products are often heavily modified, however, through methylation, epimerization, hydroxylation, heterocyclization, oxidative cross-linking and attachment of sugars. These activities are the province of specialized enzymes (either embedded in the multidomain nonribosomal peptide synthetase structure or standalone).

Biosynthesis of L-p-hydroxyphenylglycine, a non-proteinogenic amino acid constituent of peptide antibiotics.

BACKGROUND: The non-proteinogenic amino acid p-hydroxyphenylglycine is a crucial component of certain peptidic natural products synthesized by a non-ribosomal peptide synthetase mechanism. In particular, for the vancomycin group of antibiotics p-hydroxyphenylglycine plays a structural role in formation of the rigid conformation of the central heptapeptide aglycone in addition to being the site of glycosylation. Initial labeling studies suggested tyrosine was a precursor of p-hydroxyphenylglycine but the specific steps in p-hydroxyphenylglycine biosynthesis remained unknown. Recently, the sequencing of the chloroeremomycin gene cluster from Amycolatopsis orientalis gave new insights into the biosynthetic pathway and allowed for the prediction of a four enzyme pathway leading to L-p-hydroxyphenylglycine from the common metabolite prephenate. RESULTS: We have characterized three of the four proposed enzymes of the L-p-hydroxyphenylglycine biosynthetic pathway. The three enzymes are encoded by open reading frames (ORFs) 21, 22 and 17 (ORF21: [PCZA361.1, O52791, CAA11761]; ORF22: [PCZA361. 2, O52792, CAA11762]; ORF17: [PCZA361.25, O52815, CAA11790]), of the chloroeremomycin biosynthetic gene cluster and we show they have p-hydroxymandelate synthase, p-hydroxymandelate oxidase and L-p-hydroxyphenylglycine transaminase activities, respectively. CONCLUSIONS: The L-p-hydroxyphenylglycine biosynthetic pathway shown here is proposed to be the paradigm for how this non-proteinogenic amino acid is synthesized by microorganisms incorporating it into peptidic natural products. This conclusion is supported by the finding of homologs for the four L-p-hydroxyphenylpyruvate biosynthetic enzymes in four organisms known to synthesize peptidic natural products that contain p-hydroxyphenylglycine. Three of the enzymes are proposed to function in a cyclic manner in vivo with L-tyrosine being both the amino donor for L-p-hydroxyphenylglycine and a source of p-hydroxyphenylpyruvate, an intermediate in the biosynthetic pathway.

The effect of lithium carbonate on affect, mood, and personality of normal subjects.

Data reflecting affect, mood, and personality attributes of 23 normal men were compared after two weeks of placebo administration and two weeks of therapeutic serum lithium levels (mean, 0.91 mEq/liter). The study was a placebo-controlled, split-half crossover, double-blind design. Affect and mood were measured by three self-rating instruments, independent rater observation, and by the subjects' "significant others." Two personality inventories were administered. Substantial affect and mood changes are induced by lithium carbonate. Lethargy, dysphoria, a loss of interest in interacting with others and the environment, and a state of increased mental confusion were reported. No generalized effects were found in the responses to ther personality inventories.

The effect of lithium carbonate on the cognitive functions of normal subjects.

The responses of 24 normal male subjects were compared after weeks of placebo administration and two weeks of lithium carbonate administration (mean serum lithium level, 0.9 mEq/liter) on a series of tasks of intellectual function, aesthetic judgement, and semantic creativity. This was a placebo-controlled, split-half crossover, double-blind design. There were no significant changes on semantic creativity or aesthetic perception measures following lithium carbonate maintenance. There were lithium carbonate-related performance deficits on three of five performance tasks concerned with cognitive and/or motor functions. The deficit is probably due to a lithium carbonate-induced slowing of performance, consistent with our previous report of subjective effects in normal subjects. The implications of slowing on possible behavioral mediating mechanisms by which lithium carbonate exerts its clinical effects are discussed.

Identification of severe coronary artery disease using simple clinical parameters.

The purpose of our study was to examine the ability of clinical and resting electrocardiographic variables to provide useful estimates of the probability of three-vessel or left-main coronary artery disease. The study group consisted of 680 patients with symptomatic coronary artery disease who underwent exercise equilibrium radionuclide angiography and coronary angiography within 6 months. Sixteen clinical and electrocardiographic variables were examined by logistic regression analysis. The independently predictive variables were then used to develop convenient graphic estimates of the probability of three-vessel or left-main disease and to classify patients into high-risk (greater than 35%), intermediate-risk (15-35%), or low-risk (less than 15%) groups. Five variables were independently predictive of left-main or three-vessel disease: age, typical angina, diabetes, gender, and both history and electrocardiographic evidence of a prior myocardial infarction. A single graph was constructed that displayed the probability of severe coronary artery disease as a function of a five-point cardiac risk scale, which incorporated these variables. Two hundred sixty-two patients (39% of the study group) were classified as high risk; 127 of these patients (48%) had three-vessel or left-main disease. An additional 96 patients were classified as low risk; nine of these patients (9%) had three-vessel or left-main disease. Five clinical variables that were obtained on an initial patient assessment can provide useful estimates of the likelihood of severe coronary disease.

Radiation, methotrexate, and white matter necrosis: laboratory evidence for neural radioprotection with preirradiation methotrexate.

To investigate the interactions between methotrexate (MTX) and irradiation of the central nervous system, adult rats were infused with MTX via the lateral cerebral ventricle either before, during, or following single fraction irradiation to the cervical spine. Single doses ranging from 1600 cGy to 3200 cGy were administered and the dose-response curve for forelimb paralysis was compared with that seen in irradiated animals which did not receive MTX. There was no effect on the dose-response curve when MTX was administered simultaneously with or following irradiation compared to radiation alone. When MTX was given prior to irradiation, however, the entire dose-response curve shifted in the direction of radioprotection by approximately 225 cGy. Histopathologic examinations were consistent with this observation, with animals pretreated with methotrexate demonstrating significantly less white matter necrosis than observed in untreated controls. Protection of normal CNS tissue from radionecrosis, and from the associated paralysis, may be achieved with preradiation methotrexate.

Source and route of exposure influence infectivity of a molecular clone of human T cell leukemia virus type I.

Infection with human T cell leukemia virus type I (HTLV-I) is typically asymptomatic, but does result in diverse diseases ranging from adult T cell leukemia to spastic neuromyelopathy. To date, differences in HTLV-I provirus structure have not been correlated with pathogenic or asymptomatic outcome of infection. Molecular clones of HTLV-I are now available and represent a powerful tool to link virus structure to pathogenesis. Present studies to explore in vivo infectivity and pathogenicity of an HTLV-I molecular clone, K30p, have utilized the rabbit as a model system. This clone was administered to neonatal or adult rabbits by several different routes and infectivity and pathogenicity were examined. Detection of antiviral humoral immune responses, presence of provirus in tissue samples, and isolation of virus in cultures of blood lymphocytes were used to establish systemic HTLV-I infection. Intramuscular, but not nervous system, exposure to K30p HTLV-I naked DNA resulted in infection. Conversely, neural exposure to T cells that had been transfected with the K30p HTLV-I DNA consistently resulted in systemic infection. Despite detection of HTLV-I provirus in brain and spinal cord of some infected rabbits, no clinical or neuropathological changes occurred. Source and route of virus exposure played a role in infectivity, but did not influence the pathogenic outcome of HTLV-I infection.

Rabbits transfused with human immunodeficiency virus type 1-infected blood develop immune deficiency with CD4+ lymphocytopenia in the absence of clear evidence for HIV type 1 infection.

Rabbits can be infected with human immunodeficiency virus (HIV-1), but no disease signs similar to acquired immunodeficiency syndrome (AIDS) have been reported to date. In our attempt to develop types of HIV-1 more virulent for rabbits, an immunodeficiency characterized by CD4+ lymphocytopenia and opportunistic infection was induced by transfusion from HIV-1-infected rabbits. The original donor was infected for 27 months; initial passage resulted in infection of two rabbits. Transfusions from these two infected rabbits. Transfusions from these two infected rabbits caused immunodeficiency in 12 recipients. One rabbit died at 3 months and a second at 8 months postransfusion with lymphocyte depletion in lymphoid organs; one of these and another of the CD4+ lymphocytopenic rabbits had opportunistic infections. Lentivirus-like particles were detected in thymus and spleen from an affected rabbit. Despite appearance of AIDS-like disease signs, antibodies to HIV-1 probes were detected in rabbits receiving passaged blood. However, RNA transcripts hybridizing with HIV-1 probes were detected in organs of some rabbits, implicating the initial HIV infection in the disease. Transfusion from uninfected donors produced no signs of immunodeficiency, which suggests the involvement of an HIV-related agent. The present data do not allow definitive characterization of the agent(s) involved in the immunodeficiency. Possibilities include activation of a rabbit retrovirus or, alternatively, development of a mutated HIV-1 strain.

Evaluation of a follow-up system in a county health department's immunization clinic.

We designed a pilot follow-up system using two mailed reminders and evaluated it for use in the immunization clinic of a relatively large county health department in Washington State. Compliance with the recommended interval for DTP immunizations increased by 33.9% in the group of children receiving two postcard reminders compared to the control group. Over half of the respondents (52%) in the control group and 28% in the intervention group reported that transportation barriers and clinic problems prevented their return.

A quantitative study of cerebral atrophy in old age and senile dementia.

Cerebral atrophy was measured by comparing brain volume and cranial capacity at necropsy on 20 severely demented patients aged 64--92 years and 18 non-demented controls of similar age. The volumes of cerebral cortex and white matter and of the lobes of the cerebral hemispheres were found by point-counting morphometry. Patients with Alzheimer type dementia aged less than 80 years mainly showed pathological cerebral atrophy with global loss of cerebral tissue (P less than 0.001) whereas over 80 years of age they generally showed selective atrophy of temporal cortex (P less than 0.005). The findings support the view that disease processes, not exaggerated age change, underlie primary neuronal dementia of Alzheimer type.

The effect of advanced old age on the neurone content of the cerebral cortex. Observations with an automatic image analyser point counting method.

The effect of advanced old age on the nerve cell content of the cerebral cortex was examined in 19 non-demented persons aged 69-95 years, using a Quantimet 720 image analysing computer to make area proportion measurements. Neurone loss around 1.0% per annum was found both in the neocortex and in the medial hippocampus. There was also significant shrinkage of neurones in the hippocampus. Macroscopic measurements of the cerebral hemispheres by means of point-counting morphometry showed a corresponding reduction in the volume of white matter amounting to about 0.8% per annum, but only a minor change in the cortex volume. This finding is consistent with the occurrence of dendritic growth of surviving neocortical neurones. By contrast, there appears to be no compensatory dendritic proliferation in the medial hippocampus since tissue atrophy was commensurate with cell loss in this region.

Self-other agreement in personality and affectivity: the role of acquaintanceship, trait visibility, and assumed similarity.

Self- and other-ratings on the Big Five and a comprehensive inventory of trait affect were obtained from 74 married couples, 136 dating couples, and 279 friendship dyads. With the exception of Surprise, all scales showed significant self-other agreement in all 3 samples, thereby establishing their convergent validity. Consistent with the trait visibility effect, however, the Big Five consistently yielded higher agreement correlations than did the affectivity scales. Conversely, the affective traits consistently showed stronger evidence of assumed similarity (i.e., the tendency for judges to rate others as similar to themselves) than did the Big Five. Cross-sample comparisons indicated that agreement was significantly higher in the married sample than in the other 2 groups; however, analyses of 3 potential moderators in the dating and friendship samples failed to identify the source of this acquaintanceship effect.